1. Field of the Invention
This invention relates to a radar having a transmission section that switches between a first frequency and a second frequency to transmit a transmission wave having one of the first frequency and the second frequency and a reception section that receives a reflected wave of the transmission wave transmitted by the transmission section, and in particular to a radar that can measure a distance to an object with a simple configuration.
2. Description of the Related Art
Hitherto, various radars have been widely used for detecting an object and measuring a distance. For example, JP-A-2002-511945 discloses an art of switching between two frequencies, transmitting the resultant waveform as a transmission wave, receiving a reflected wave having a reception lag equal to or less than the limit lag corresponding to the limit distance, and measuring the distance.
U.S. Pat. No. 5,302,956 discloses a radar whose cost is reduced by simplifying the configuration so that a received reflected wave before signal processing is digitalized and the distance is measured by performing digital signal processing.
Further, JP-A-2003-167048 discloses an art of emitting a transmission signal every given time cycle and for a short time only and further modulating the signal of a local oscillation signal source input to a mixer of a reception section so as to change the frequency like sawteeth, thereby detecting the target of an object having relative speed zero and further separating a plurality of objects having the same relative speed.